Thermostat



' March 3, 1936. L. .T. FOLSOM ET AL 2,032,358

THERMOSTAT Filed Nov. 4, 1953 Leon 7. Fo/som Jo/m R. Mac reyof U Afiorzzey Patented Mar. 3,

UNITED STATES PATENT OFFICE THERMOSTAT Leon T. Folsom, Berkeley, and John R. Mac- Gregor, Albany, Calif assignors to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application November 4, 1933, Serial No. 696,649

6 Claims.

This invention relates to a thermostat of the flexible metallic container type, in which the container is partially filled with a volatile liquid, and

is particularly directed to a balanced or compensated form in which change in ambient or atmospheric pressure, such as may be due to change in elevation of several thousand feet, will have no effect upon the calibration or setting of the thermostat mechanism.

Heretofore, thermostats of this general type have been widely known and used, and for normal changes in ambient or atmospheric pressure variation such as may be due to weather conditions their accuracy is a dequate. However, where they are used on equipment which may be subjected to abnormal changes in ambient pressure,

such as would occur whe n travelling from sea level over a high mountain pass in a railway train, or in any sort of aircraft, the variations caused thereby are serious. The common form of this thermostat balances the vapor pressure of a volatile liquid such as butane, together with some of its vapor, enclosed in a flexible metallic container or a rigid container having a movable wall, against the pressure of the atmosphere and usually a spring or other restraining force. Obviously, the

restraining effort of the stantially constant, but

spring would remain subthe restraint due to ambient or atmospheric pressure, under the conditions of change outlined above, would not remain constant. This has been found to affect seriously the setting or calibration of the temperature con-' trol mechanism controlled by such a thermostat.

For example, assume a car heater in a refrigwill reduce the effective the fruit.

In order to obviate this effect of atmospheric setting of the thermostat by as much as 4 or F., thus seriously damaging or ambient pressure variation, a second flexible metallic container is mounted to oppose the action of the first, and this second container is filled with air or some gas which, under the operating conditions, is relatively uid state. In the at normal atmospheric quently is so far from i far removed from its liqpresent case, the air used is temperature and consetS liquid state that it will follow substantially the perfect gas laws.

consequence, a change in ambient will not change the pressure in As a temperature the air filled container as rapidly as it'will the pressure in the butane filled container, which vapor-pressure temperature relation Thus a resultant or difierential' motion of the flexible or movable walls of the tained by a change in will not be as great as balancing container.

With the movable parts of it would be two containers will be obtemperature, although it without the the two containers faced toward each other and acting to oppose each other by their internal pressure changes, it is only necessary to provide a substantially rigid strut between them so that the resulting motion of the strut is proportional to the ambient temperature changes alone.

pressure from any cause will have Variations in ambient no effect on the net force resulting from the action of the two containers opposing each other and the motion of the rigid strut resulting therefrom,

as such variations will act equally and oppositely on the movable walls of the two containers,

cancelled thereby.

It is an object of thermostat of the this invention andwillbe to provide a flexible container-volatile liquid type which will be unaffected by any change in atmospheric or ambient pressure.

Another object is to provide a simple and effective thermostat construction which may be adjusted easily, and which has a moving parts.

Another object is minimum of to provide a balanced thermostat of this type in which two opposed bellows or movable walled containers are used, one filled with a nearly perfect gas in order to cancel out or counterbalance any variations which may occur in the pressure of the ambient fluid.

' These and other objects and advantages will become apparent from the description which follows, and from the accompanying drawing, which forms a part of this specification and illustrates a preferred embodiment of the invention.

In the drawing:

Figure 1 is a front mostat embodying this invention.

Figure 2 is a section on line elevation of a balanced therlI-II of Figure 1,

showing the opposed movable walled metallic containers and the spring restraining and adjusting means.

Figure 3 is a section on line III-III of Figu e 1; the thermostat to a showing an application of rotatable shaft which may be use contacts or a valve, etc.

d to control latter will follow the 5 40 A connecting strut 33 extends between the inonly to ambient p Referring to the drawing, the numeral l rep- 49 extending inwardly from side plate l2 and resents a rigid box frame or body provided with passing through a slot 50 in the lever. opposite side plates II and I 2. These are cut The precise operating temperature setting of away as at I3 and I 4, respectively, to allow the the thermostat is accomplished by cam 48 mount- 5 operating mechanism, which will be described ed on shaft 5| and bearing against the'free end of 5 below, to pass across the center of the frame. lever 46. Shaft 5| passes through bearing52inthe Movable walled container I5, which comprises front of frame It and has an adjusting and tema rigid flanged shell l6 and a flexible metallic perature indicating arm 53 on its outer end. Arm bellows I1, is mounted on plate II as by screws I8 53 moves over the face of the calibrated semi- 10 at the four corners of shell Hi. The inner face of circular dial plate 54, and is provided with a re- 10 flexible metallic bellows I1 is provided with a cessed spring 55 which urges ball 56 outwardly filling tube l9, sealed by soldering at 20, and'has to seat in any one of the'spaced recesses 51 in a tube protecting shield or cylinder 2|. The .dial plate 54, so that anygiven temperature setoutcr edge of bellows I1 is sealed to shell I 6 as by ting will be maintained in spite of shocks and soldering at 22. In this example, the container jars. 15

tains both liquid and butane vapor 24 (not ment of the thermostat is made by screw 41 acting shown). Butane is described in this example, inon the outer end of lever 46. This gives the asmuch as its vapor pressure at 32 F., at which approximate temperature at which the spring rerange this particular thermostat is intended to strained balanced flexible bellows l1 and 21 will 20 25 sirable. cam 48 to give the delicate and accurate changes 25 v Movable walled container 25 is similar in conin the thrust of restraining spring 45 which deterstruction to container IS, with a rigid flanged mines the precise operating position of the control shell 26, and a flexible metallic bellows 21, the mechanism. shell fastened to plate I2 with machine screws 28. It is obvious that other combinations of fluids The bellows 21 is similarly provided with a filling could be utilized in the two opposed flexible con- 30 tube 29 which has a protecting shield 30, and is tainers of this device, depending on the condijoined to shell 26 by soldering as at 3|. This tions under which the thermostat is to be opcontainer 25, however, is'fllled with dry air 32 at erated. The essential feature of the invention, substantially atmospheric pressure. While air is however, appears to reside in the provision of two 35 used in this example, some other gas which folsuch opposed containers, with dissimilar fluids 35 lows a substantially different temperature-prestherein whose temperature-pressure .charactersure law than the liquid and vapor in container istics are such that one will respond both to stances under which the device is to operate. changes, while the other will respond substantially chang ner faces of metallic bellows l1 and 21 and is ultimate result will be aresponse only toambient recessed at each end to flt over the shields 2 I and temperature changes by a resultant motion of the 30, which serve to center the strut. Approxlmovable walls of the containers. mately midway between the bellows is a groove Although aspeciflc construction em this 34 in strut 33 in which a crank arm 35 on control invention has been described and illustrated, it is 45 rod 35 is adapted to be received. In this examto be understood that the invention is not limited ainst one shoulder of groove 34, as shown. We claim: 60 Spring 31 may also serve to open or close the 1. A thermostat of the type described, comprisvalve, contact mechanism, etc., (not shown) which ing two spaced flexible'containers, the flexible remainder of groove 34 may conveniently provide to ambient temperature d Pressure anges 55 00 Rod 36 maybe supported and guided ants lower :ontainers due to a change in ambient temperaframe In a volatile liquid and its vapor in onecontainer, a 65 which the containers l5 and 25 may operate, a

metallic bellows '21 and an adjusting lever 45 containers due to a change in nt; t 70 5* from transverse displacement by a guide member sealed containers each having a movable wall aoaaass exposed to said ambient fluid, one of said containers being filled with the said fluid in which the thermostat; is to be immersed, said other container being filled with a fluid whose pressuretemperature characteristic is appreciably different from said first named fluid, and operating means responsive to the resultant movement of the movable walls of said containers due to a change in ambient temperature.

4. A thermostat of the type described, comprising two spaced sealed containers each having a movable wall exposed to the ambient medium whose temperature is to be controlled, a volatile liquid and its vapor in one container, a normally fixed gas in said other container, resilient means opposing a movement of one of said movable walls, and means rigidly connecting said movable walls and responsive to a resultant movement thereof due to a change in ambient temperature.

5. A thermostat of the type described, comprising two spaced sealed containers each having a movable wall exposed to the ambient medium whose temperature is to be controlled, a volatile liquid and its gas in one container, a normally fixed gas in said other container, resilient means opposing a movement of one of said movable walls, means for adjusting the restraining efiort of said resilient means, and operating means connecting said movable walls and responsive to a resultant movement thereof due to a change in ambient temperature.

6. A thermostat of the type described, comprising two spaced sealed containers each having a movable wall exposed to the ambient medium whose temperature is to becontrolled, a volatile liquid and its gas in one container, a normally fixed gas in said other container, resilient means opposing a movement of one of said movable walls, means for adjusting the restraining efiort of said resilient means, and means connecting said movable walls and responsive to a resultant movement thereof due to a change in ambient temperature, said last named means adapted to be connected to an ambient temperature controlling device, whereby said temperature may be maintained in a definite range.

LEON T. FOLSOM. JOHN R. MACGREGOR. 

